Message 321352 - Python tracker

I realize now that calling self.fail at https://hg.python.org/cpython/rev/74e79b2c114a#l2.20 is a problem: self is an instance of the C class, not the TestCase instance.

(The line is unreachable anyway so this doesn’t matter a lot.  In other projects I’d use something like `__reduce__ = raiser(AssertionError)` to avoid this.)